/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.ta.common;

import android.annotation.TargetApi;
import android.os.Handler;
import android.os.Message;
import android.os.Process;

import java.util.ArrayDeque;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import com.ta.common.AndroidVersionCheckUtils;

/**
 * ************************************* Copied from JB release framework:
 * https:
 * //android.googlesource.com/platform/frameworks/base/+/jb-release/core/java
 * /android/os/AsyncTask.java
 * 
 * so that threading behavior on all OS versions is the same and we can tweak
 * behavior by using executeOnExecutor() if needed.
 * 
 * There are 3 changes in this copy of AsyncTask: -pre-HC a single thread
 * executor is used for serial operation (Executors.newSingleThreadExecutor) and
 * is the default -the default THREAD_POOL_EXECUTOR was changed to use
 * DiscardOldestPolicy -a new fixed thread pool called DUAL_THREAD_EXECUTOR was
 * added *************************************
 * 
 * <p>
 * AsyncTask enables proper and easy use of the UI thread. This class allows to
 * perform background operations and publish results on the UI thread without
 * having to manipulate threads and/or handlers.
 * </p>
 * 
 * <p>
 * AsyncTask is designed to be a helper class around {@link Thread} and
 * {@link Handler} and does not constitute a generic threading framework.
 * AsyncTasks should ideally be used for short operations (a few seconds at the
 * most.) If you need to keep threads running for long periods of time, it is
 * highly recommended you use the various APIs provided by the
 * <code>java.util.concurrent</code> pacakge such as {@link Executor},
 * {@link ThreadPoolExecutor} and {@link FutureTask}.
 * </p>
 * 
 * <p>
 * An asynchronous task is defined by a computation that runs on a background
 * thread and whose result is published on the UI thread. An asynchronous task
 * is defined by 3 generic types, called <code>Params</code>,
 * <code>Progress</code> and <code>Result</code>, and 4 steps, called
 * <code>onPreExecute</code>, <code>doInBackground</code>,
 * <code>onProgressUpdate</code> and <code>onPostExecute</code>.
 * </p>
 * 
 * <div class="special reference"> <h3>Developer Guides</h3>
 * <p>
 * For more information about using tasks and threads, read the <a
 * href="{@docRoot}
 * guide/topics/fundamentals/processes-and-threads.html">Processes and
 * Threads</a> developer guide.
 * </p>
 * </div>
 * 
 * <h2>Usage</h2>
 * <p>
 * AsyncTask must be subclassed to be used. The subclass will override at least
 * one method ({@link #doInBackground}), and most often will override a second
 * one ({@link #onPostExecute}.)
 * </p>
 * 
 * <p>
 * Here is an example of subclassing:
 * </p>
 * 
 * <pre class="prettyprint">
 * private class DownloadFilesTask extends AsyncTask&lt;URL, Integer, Long&gt;
 * {
 * 	protected Long doInBackground(URL... urls)
 * 	{
 * 		int count = urls.length;
 * 		long totalSize = 0;
 * 		for (int i = 0; i &lt; count; i++)
 * 		{
 * 			totalSize += Downloader.downloadFile(urls[i]);
 * 			publishProgress((int) ((i / (float) count) * 100));
 * 			// Escape early if cancel() is called
 * 			if (isCancelled())
 * 				break;
 * 		}
 * 		return totalSize;
 * 	}
 * 
 * 	protected void onProgressUpdate(Integer... progress)
 * 	{
 * 		setProgressPercent(progress[0]);
 * 	}
 * 
 * 	protected void onPostExecute(Long result)
 * 	{
 * 		showDialog(&quot;Downloaded &quot; + result + &quot; bytes&quot;);
 * 	}
 * }
 * </pre>
 * 
 * <p>
 * Once created, a task is executed very simply:
 * </p>
 * 
 * <pre class="prettyprint">
 * new DownloadFilesTask().execute(url1, url2, url3);
 * </pre>
 * 
 * <h2>AsyncTask's generic types</h2>
 * <p>
 * The three types used by an asynchronous task are the following:
 * </p>
 * <ol>
 * <li><code>Params</code>, the type of the parameters sent to the task upon
 * execution.</li>
 * <li><code>Progress</code>, the type of the progress units published during
 * the background computation.</li>
 * <li><code>Result</code>, the type of the result of the background
 * computation.</li>
 * </ol>
 * <p>
 * Not all types are always used by an asynchronous task. To mark a type as
 * unused, simply use the type {@link Void}:
 * </p>
 * 
 * <pre>
 * private class MyTask extends AsyncTask&lt;Void, Void, Void&gt; { ... }
 * </pre>
 * 
 * <h2>The 4 steps</h2>
 * <p>
 * When an asynchronous task is executed, the task goes through 4 steps:
 * </p>
 * <ol>
 * <li>{@link #onPreExecute()}, invoked on the UI thread immediately after the
 * task is executed. This step is normally used to setup the task, for instance
 * by showing a progress bar in the user interface.</li>
 * <li>{@link #doInBackground}, invoked on the background thread immediately
 * after {@link #onPreExecute()} finishes executing. This step is used to
 * perform background computation that can take a long time. The parameters of
 * the asynchronous task are passed to this step. The result of the computation
 * must be returned by this step and will be passed back to the last step. This
 * step can also use {@link #publishProgress} to publish one or more units of
 * progress. These values are published on the UI thread, in the
 * {@link #onProgressUpdate} step.</li>
 * <li>{@link #onProgressUpdate}, invoked on the UI thread after a call to
 * {@link #publishProgress}. The timing of the execution is undefined. This
 * method is used to display any form of progress in the user interface while
 * the background computation is still executing. For instance, it can be used
 * to animate a progress bar or show logs in a text field.</li>
 * <li>{@link #onPostExecute}, invoked on the UI thread after the background
 * computation finishes. The result of the background computation is passed to
 * this step as a parameter.</li>
 * </ol>
 * 
 * <h2>Cancelling a task</h2>
 * <p>
 * A task can be cancelled at any time by invoking {@link #cancel(boolean)}.
 * Invoking this method will cause subsequent calls to {@link #isCancelled()} to
 * return true. After invoking this method, {@link #onCancelled(Object)},
 * instead of {@link #onPostExecute(Object)} will be invoked after
 * {@link #doInBackground(Object[])} returns. To ensure that a task is cancelled
 * as quickly as possible, you should always check the return value of
 * {@link #isCancelled()} periodically from {@link #doInBackground(Object[])},
 * if possible (inside a loop for instance.)
 * </p>
 * 
 * <h2>Threading rules</h2>
 * <p>
 * There are a few threading rules that must be followed for this class to work
 * properly:
 * </p>
 * <ul>
 * <li>The AsyncTask class must be loaded on the UI thread. This is done
 * automatically as of {@link android.os.Build.VERSION_CODES#JELLY_BEAN}.</li>
 * <li>The task instance must be created on the UI thread.</li>
 * <li>{@link #execute} must be invoked on the UI thread.</li>
 * <li>Do not call {@link #onPreExecute()}, {@link #onPostExecute},
 * {@link #doInBackground}, {@link #onProgressUpdate} manually.</li>
 * <li>The task can be executed only once (an exception will be thrown if a
 * second execution is attempted.)</li>
 * </ul>
 * 
 * <h2>Memory observability</h2>
 * <p>
 * AsyncTask guarantees that all callback calls are synchronized in such a way
 * that the following operations are safe without explicit synchronizations.
 * </p>
 * <ul>
 * <li>Set member fields in the constructor or {@link #onPreExecute}, and refer
 * to them in {@link #doInBackground}.
 * <li>Set member fields in {@link #doInBackground}, and refer to them in
 * {@link #onProgressUpdate} and {@link #onPostExecute}.
 * </ul>
 * 
 * <h2>Order of execution</h2>
 * <p>
 * When first introduced, AsyncTasks were executed serially on a single
 * background thread. Starting with {@link android.os.Build.VERSION_CODES#DONUT}
 * , this was changed to a pool of threads allowing multiple tasks to operate in
 * parallel. Starting with {@link android.os.Build.VERSION_CODES#HONEYCOMB},
 * tasks are executed on a single thread to avoid common application errors
 * caused by parallel execution.
 * </p>
 * <p>
 * If you truly want parallel execution, you can invoke
 * {@link #executeOnExecutor(java.util.concurrent.Executor, Object[])} with
 * {@link #THREAD_POOL_EXECUTOR}.
 * </p>
 */
public abstract class AsyncTask<Params, Progress, Result>
{
	private static final String LOG_TAG = "AsyncTask";

	private static final int CORE_POOL_SIZE = 5;
	private static final int MAXIMUM_POOL_SIZE = 128;
	private static final int KEEP_ALIVE = 1;

	private static final ThreadFactory sThreadFactory = new ThreadFactory()
	{
		private final AtomicInteger mCount = new AtomicInteger(1);

		public Thread newThread(Runnable r)
		{
			return new Thread(r, "AsyncTask #" + mCount.getAndIncrement());
		}
	};

	private static final BlockingQueue<Runnable> sPoolWorkQueue = new LinkedBlockingQueue<Runnable>(
			10);

	/**
	 * An {@link Executor} that can be used to execute tasks in parallel.
	 */
	public static final Executor THREAD_POOL_EXECUTOR = new ThreadPoolExecutor(
			CORE_POOL_SIZE, MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS,
			sPoolWorkQueue, sThreadFactory,
			new ThreadPoolExecutor.DiscardOldestPolicy());

	/**
	 * An {@link Executor} that executes tasks one at a time in serial order.
	 * This serialization is global to a particular process.
	 */
	public static final Executor SERIAL_EXECUTOR = AndroidVersionCheckUtils
			.hasHoneycomb() ? new SerialExecutor() : Executors
			.newSingleThreadExecutor(sThreadFactory);

	public static final Executor DUAL_THREAD_EXECUTOR = Executors
			.newFixedThreadPool(2, sThreadFactory);

	private static final int MESSAGE_POST_RESULT = 0x1;
	private static final int MESSAGE_POST_PROGRESS = 0x2;

	private static final InternalHandler sHandler = new InternalHandler();

	private static volatile Executor sDefaultExecutor = SERIAL_EXECUTOR;
	private final WorkerRunnable<Params, Result> mWorker;
	private final FutureTask<Result> mFuture;

	private volatile Status mStatus = Status.PENDING;

	private final AtomicBoolean mCancelled = new AtomicBoolean();
	private final AtomicBoolean mTaskInvoked = new AtomicBoolean();

	@TargetApi(11)
	private static class SerialExecutor implements Executor
	{
		final ArrayDeque<Runnable> mTasks = new ArrayDeque<Runnable>();
		Runnable mActive;

		public synchronized void execute(final Runnable r)
		{
			mTasks.offer(new Runnable()
			{
				public void run()
				{
					try
					{
						r.run();
					} finally
					{
						scheduleNext();
					}
				}
			});
			if (mActive == null)
			{
				scheduleNext();
			}
		}

		protected synchronized void scheduleNext()
		{
			if ((mActive = mTasks.poll()) != null)
			{
				THREAD_POOL_EXECUTOR.execute(mActive);
			}
		}
	}

	/**
	 * Indicates the current status of the task. Each status will be set only
	 * once during the lifetime of a task.
	 */
	public enum Status
	{
		/**
		 * Indicates that the task has not been executed yet.
		 */
		PENDING,
		/**
		 * Indicates that the task is running.
		 */
		RUNNING,
		/**
		 * Indicates that {@link AsyncTask#onPostExecute} has finished.
		 */
		FINISHED,
	}

	/** @hide Used to force static handler to be created. */
	public static void init()
	{
		sHandler.getLooper();
	}

	/** @hide */
	public static void setDefaultExecutor(Executor exec)
	{
		sDefaultExecutor = exec;
	}

	/**
	 * Creates a new asynchronous task. This constructor must be invoked on the
	 * UI thread.
	 */
	public AsyncTask()
	{
		mWorker = new WorkerRunnable<Params, Result>()
		{
			public Result call() throws Exception
			{
				mTaskInvoked.set(true);

				Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
				// noinspection unchecked
				return postResult(doInBackground(mParams));
			}
		};

		mFuture = new FutureTask<Result>(mWorker)
		{
			@Override
			protected void done()
			{
				try
				{
					postResultIfNotInvoked(get());
				} catch (InterruptedException e)
				{
					android.util.Log.w(LOG_TAG, e);
				} catch (ExecutionException e)
				{
					throw new RuntimeException(
							"An error occured while executing doInBackground()",
							e.getCause());
				} catch (CancellationException e)
				{
					postResultIfNotInvoked(null);
				}
			}
		};
	}

	private void postResultIfNotInvoked(Result result)
	{
		final boolean wasTaskInvoked = mTaskInvoked.get();
		if (!wasTaskInvoked)
		{
			postResult(result);
		}
	}

	private Result postResult(Result result)
	{
		@SuppressWarnings("unchecked")
		Message message = sHandler.obtainMessage(MESSAGE_POST_RESULT,
				new AsyncTaskResult<Result>(this, result));
		message.sendToTarget();
		return result;
	}

	/**
	 * Returns the current status of this task.
	 * 
	 * @return The current status.
	 */
	public final Status getStatus()
	{
		return mStatus;
	}

	/**
	 * Override this method to perform a computation on a background thread. The
	 * specified parameters are the parameters passed to {@link #execute} by the
	 * caller of this task.
	 * 
	 * This method can call {@link #publishProgress} to publish updates on the
	 * UI thread.
	 * 
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return A result, defined by the subclass of this task.
	 * 
	 * @see #onPreExecute()
	 * @see #onPostExecute
	 * @see #publishProgress
	 */
	protected abstract Result doInBackground(Params... params);

	/**
	 * Runs on the UI thread before {@link #doInBackground}.
	 * 
	 * @see #onPostExecute
	 * @see #doInBackground
	 */
	protected void onPreExecute()
	{
	}

	/**
	 * <p>
	 * Runs on the UI thread after {@link #doInBackground}. The specified result
	 * is the value returned by {@link #doInBackground}.
	 * </p>
	 * 
	 * <p>
	 * This method won't be invoked if the task was cancelled.
	 * </p>
	 * 
	 * @param result
	 *            The result of the operation computed by
	 *            {@link #doInBackground}.
	 * 
	 * @see #onPreExecute
	 * @see #doInBackground
	 * @see #onCancelled(Object)
	 */
	@SuppressWarnings(
	{ "UnusedDeclaration" })
	protected void onPostExecute(Result result)
	{
	}

	/**
	 * Runs on the UI thread after {@link #publishProgress} is invoked. The
	 * specified values are the values passed to {@link #publishProgress}.
	 * 
	 * @param values
	 *            The values indicating progress.
	 * 
	 * @see #publishProgress
	 * @see #doInBackground
	 */
	@SuppressWarnings(
	{ "UnusedDeclaration" })
	protected void onProgressUpdate(Progress... values)
	{
	}

	/**
	 * <p>
	 * Runs on the UI thread after {@link #cancel(boolean)} is invoked and
	 * {@link #doInBackground(Object[])} has finished.
	 * </p>
	 * 
	 * <p>
	 * The default implementation simply invokes {@link #onCancelled()} and
	 * ignores the result. If you write your own implementation, do not call
	 * <code>super.onCancelled(result)</code>.
	 * </p>
	 * 
	 * @param result
	 *            The result, if any, computed in
	 *            {@link #doInBackground(Object[])}, can be null
	 * 
	 * @see #cancel(boolean)
	 * @see #isCancelled()
	 */
	@SuppressWarnings(
	{ "UnusedParameters" })
	protected void onCancelled(Result result)
	{
		onCancelled();
	}

	/**
	 * <p>
	 * Applications should preferably override {@link #onCancelled(Object)}.
	 * This method is invoked by the default implementation of
	 * {@link #onCancelled(Object)}.
	 * </p>
	 * 
	 * <p>
	 * Runs on the UI thread after {@link #cancel(boolean)} is invoked and
	 * {@link #doInBackground(Object[])} has finished.
	 * </p>
	 * 
	 * @see #onCancelled(Object)
	 * @see #cancel(boolean)
	 * @see #isCancelled()
	 */
	protected void onCancelled()
	{
	}

	/**
	 * Returns <tt>true</tt> if this task was cancelled before it completed
	 * normally. If you are calling {@link #cancel(boolean)} on the task, the
	 * value returned by this method should be checked periodically from
	 * {@link #doInBackground(Object[])} to end the task as soon as possible.
	 * 
	 * @return <tt>true</tt> if task was cancelled before it completed
	 * 
	 * @see #cancel(boolean)
	 */
	public final boolean isCancelled()
	{
		return mCancelled.get();
	}

	/**
	 * <p>
	 * Attempts to cancel execution of this task. This attempt will fail if the
	 * task has already completed, already been cancelled, or could not be
	 * cancelled for some other reason. If successful, and this task has not
	 * started when <tt>cancel</tt> is called, this task should never run. If
	 * the task has already started, then the <tt>mayInterruptIfRunning</tt>
	 * parameter determines whether the thread executing this task should be
	 * interrupted in an attempt to stop the task.
	 * </p>
	 * 
	 * <p>
	 * Calling this method will result in {@link #onCancelled(Object)} being
	 * invoked on the UI thread after {@link #doInBackground(Object[])} returns.
	 * Calling this method guarantees that {@link #onPostExecute(Object)} is
	 * never invoked. After invoking this method, you should check the value
	 * returned by {@link #isCancelled()} periodically from
	 * {@link #doInBackground(Object[])} to finish the task as early as
	 * possible.
	 * </p>
	 * 
	 * @param mayInterruptIfRunning
	 *            <tt>true</tt> if the thread executing this task should be
	 *            interrupted; otherwise, in-progress tasks are allowed to
	 *            complete.
	 * 
	 * @return <tt>false</tt> if the task could not be cancelled, typically
	 *         because it has already completed normally; <tt>true</tt>
	 *         otherwise
	 * 
	 * @see #isCancelled()
	 * @see #onCancelled(Object)
	 */
	public final boolean cancel(boolean mayInterruptIfRunning)
	{
		mCancelled.set(true);
		return mFuture.cancel(mayInterruptIfRunning);
	}

	/**
	 * Waits if necessary for the computation to complete, and then retrieves
	 * its result.
	 * 
	 * @return The computed result.
	 * 
	 * @throws CancellationException
	 *             If the computation was cancelled.
	 * @throws ExecutionException
	 *             If the computation threw an exception.
	 * @throws InterruptedException
	 *             If the current thread was interrupted while waiting.
	 */
	public final Result get() throws InterruptedException, ExecutionException
	{
		return mFuture.get();
	}

	/**
	 * Waits if necessary for at most the given time for the computation to
	 * complete, and then retrieves its result.
	 * 
	 * @param timeout
	 *            Time to wait before cancelling the operation.
	 * @param unit
	 *            The time unit for the timeout.
	 * 
	 * @return The computed result.
	 * 
	 * @throws CancellationException
	 *             If the computation was cancelled.
	 * @throws ExecutionException
	 *             If the computation threw an exception.
	 * @throws InterruptedException
	 *             If the current thread was interrupted while waiting.
	 * @throws TimeoutException
	 *             If the wait timed out.
	 */
	public final Result get(long timeout, TimeUnit unit)
			throws InterruptedException, ExecutionException, TimeoutException
	{
		return mFuture.get(timeout, unit);
	}

	/**
	 * Executes the task with the specified parameters. The task returns itself
	 * (this) so that the caller can keep a reference to it.
	 * 
	 * <p>
	 * Note: this function schedules the task on a queue for a single background
	 * thread or pool of threads depending on the platform version. When first
	 * introduced, AsyncTasks were executed serially on a single background
	 * thread. Starting with {@link android.os.Build.VERSION_CODES#DONUT}, this
	 * was changed to a pool of threads allowing multiple tasks to operate in
	 * parallel. Starting {@link android.os.Build.VERSION_CODES#HONEYCOMB},
	 * tasks are back to being executed on a single thread to avoid common
	 * application errors caused by parallel execution. If you truly want
	 * parallel execution, you can use the {@link #executeOnExecutor} version of
	 * this method with {@link #THREAD_POOL_EXECUTOR}; however, see commentary
	 * there for warnings on its use.
	 * 
	 * <p>
	 * This method must be invoked on the UI thread.
	 * 
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return This instance of AsyncTask.
	 * 
	 * @throws IllegalStateException
	 *             If {@link #getStatus()} returns either
	 *             {@link AsyncTask.Status#RUNNING} or
	 *             {@link AsyncTask.Status#FINISHED}.
	 * 
	 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
	 * @see #execute(Runnable)
	 */
	public final AsyncTask<Params, Progress, Result> execute(Params... params)
	{
		return executeOnExecutor(sDefaultExecutor, params);
	}

	/**
	 * Executes the task with the specified parameters. The task returns itself
	 * (this) so that the caller can keep a reference to it.
	 * 
	 * <p>
	 * This method is typically used with {@link #THREAD_POOL_EXECUTOR} to allow
	 * multiple tasks to run in parallel on a pool of threads managed by
	 * AsyncTask, however you can also use your own {@link Executor} for custom
	 * behavior.
	 * 
	 * <p>
	 * <em>Warning:</em> Allowing multiple tasks to run in parallel from a
	 * thread pool is generally <em>not</em> what one wants, because the order
	 * of their operation is not defined. For example, if these tasks are used
	 * to modify any state in common (such as writing a file due to a button
	 * click), there are no guarantees on the order of the modifications.
	 * Without careful work it is possible in rare cases for the newer version
	 * of the data to be over-written by an older one, leading to obscure data
	 * loss and stability issues. Such changes are best executed in serial; to
	 * guarantee such work is serialized regardless of platform version you can
	 * use this function with {@link #SERIAL_EXECUTOR}.
	 * 
	 * <p>
	 * This method must be invoked on the UI thread.
	 * 
	 * @param exec
	 *            The executor to use. {@link #THREAD_POOL_EXECUTOR} is
	 *            available as a convenient process-wide thread pool for tasks
	 *            that are loosely coupled.
	 * @param params
	 *            The parameters of the task.
	 * 
	 * @return This instance of AsyncTask.
	 * 
	 * @throws IllegalStateException
	 *             If {@link #getStatus()} returns either
	 *             {@link AsyncTask.Status#RUNNING} or
	 *             {@link AsyncTask.Status#FINISHED}.
	 * 
	 * @see #execute(Object[])
	 */
	public final AsyncTask<Params, Progress, Result> executeOnExecutor(
			Executor exec, Params... params)
	{
		if (mStatus != Status.PENDING)
		{
			switch (mStatus)
			{
			case RUNNING:
				throw new IllegalStateException("Cannot execute task:"
						+ " the task is already running.");
			case FINISHED:
				throw new IllegalStateException("Cannot execute task:"
						+ " the task has already been executed "
						+ "(a task can be executed only once)");
			}
		}

		mStatus = Status.RUNNING;

		onPreExecute();

		mWorker.mParams = params;
		exec.execute(mFuture);

		return this;
	}

	/**
	 * Convenience version of {@link #execute(Object...)} for use with a simple
	 * Runnable object. See {@link #execute(Object[])} for more information on
	 * the order of execution.
	 * 
	 * @see #execute(Object[])
	 * @see #executeOnExecutor(java.util.concurrent.Executor, Object[])
	 */
	public static void execute(Runnable runnable)
	{
		sDefaultExecutor.execute(runnable);
	}

	/**
	 * This method can be invoked from {@link #doInBackground} to publish
	 * updates on the UI thread while the background computation is still
	 * running. Each call to this method will trigger the execution of
	 * {@link #onProgressUpdate} on the UI thread.
	 * 
	 * {@link #onProgressUpdate} will note be called if the task has been
	 * canceled.
	 * 
	 * @param values
	 *            The progress values to update the UI with.
	 * 
	 * @see #onProgressUpdate
	 * @see #doInBackground
	 */
	protected final void publishProgress(Progress... values)
	{
		if (!isCancelled())
		{
			sHandler.obtainMessage(MESSAGE_POST_PROGRESS,
					new AsyncTaskResult<Progress>(this, values)).sendToTarget();
		}
	}

	private void finish(Result result)
	{
		if (isCancelled())
		{
			onCancelled(result);
		} else
		{
			onPostExecute(result);
		}
		mStatus = Status.FINISHED;
	}

	private static class InternalHandler extends Handler
	{
		@SuppressWarnings(
		{ "unchecked", "RawUseOfParameterizedType" })
		@Override
		public void handleMessage(Message msg)
		{
			AsyncTaskResult result = (AsyncTaskResult) msg.obj;
			switch (msg.what)
			{
			case MESSAGE_POST_RESULT:
				// There is only one result
				result.mTask.finish(result.mData[0]);
				break;
			case MESSAGE_POST_PROGRESS:
				result.mTask.onProgressUpdate(result.mData);
				break;
			}
		}
	}

	private static abstract class WorkerRunnable<Params, Result> implements
			Callable<Result>
	{
		Params[] mParams;
	}

	@SuppressWarnings(
	{ "RawUseOfParameterizedType" })
	private static class AsyncTaskResult<Data>
	{
		final AsyncTask mTask;
		final Data[] mData;

		AsyncTaskResult(AsyncTask task, Data... data)
		{
			mTask = task;
			mData = data;
		}
	}
}